Owners of 2016-2018 Cadillac XTS vehicles equipped with an LF3 engine may comment that a vibration is felt under heavy acceleration around 20 miles-per-hour which can be felt in the seat.
This condition may be caused by a second-order vibration from the cardan joint. If this is verified, install 4.5mm-thick shims P/N 11562546 on top of the front RDM isolator bushings.
Remove one of the front differential bolts. Loosen the opposite side front differential mount bolt. Position the flat washer over the differential mount washer. Loosely install the bolt enough to support the differential.
Remove the other front differential bolt and position the washer over the differential mount washer and install the bolt. Tighten both bolts to service manual specifications.
